T. F. Cooper duplex

Discussion in 'European & Other Pocket Watches' started by Travler1, Aug 11, 2019.

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  1. Travler1

    Travler1 Registered User
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    Hello all, I wanted to share my discovery and upcoming adventure with the included pictured watch. Hopefully it will be entertainment and knowledge for those interested. I have owned this watch since the very early 1980’s ..purchased in a cache of pockets from a gold scraper ( who didn’t want to scrap em ) gold was in the $200’s after peaking to $800 or so ....anyway the dealer sold me the “lot” of pocket watch’s for $125.00 each .....large and small 10k-18k ....take all or none.

    It is only via my accumulated knowledge shared by members on this site that I am able to post this watch I wish to thank John, Graham and Omexa for there previous posts on T. F. Cooper .

    I believe the photos mostly speak for themself. However, one cannot see the duplex escapement wheel or possibly more interesting..... down in the cave.a gleam of red. I’m not sure if I’m looking at the impulse jewel or by chance a ruby roller.

    The balance on this watch is free and will spin for 2 seconds or so ....however it is wound tight. So it’s off tomorrow for bench work ....I will be pleased to post photos of exactly what’s what upon disassembly.

    I would very much appreciate any thoughts on a ruby roller and cautions for disassembly ...regards to all. 95E90A64-CF49-4534-81E6-04257DFC6683.png 75D01671-43A4-49DB-B5B9-74BF132E05C4.png

    9E6505B2-1021-410B-8FDF-B236FB450D35.jpeg
     
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  2. Travler1

    Travler1 Registered User
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    B4C0AAAA-A1A7-4EFB-A92C-908DCE6A9332.png .....having a hard time with photos ....ehhhhh
     
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  3. gmorse

    gmorse Registered User
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    Hi Travler1,

    Unlike so many Coopers we see, this is certainly the real thing! All English duplexes started off life with a ruby locking roller but relatively few had a ruby in the impulse roller.

    Because the escape wheel acts directly on the balance, you'll have to make sure the mainspring and the maintaining power, (if it has that, which looks likely), are both completely let down before you remove the balance.

    I can't find an entry for an 'EM' incuse in Priestley's London list, and the dome doesn't have a complete set of marks, hence no date letter, but it must be prior to 1822 because the leopard has a crown. It could conceivably be a Chester assay, since the leopard also appears there, but the only possible person there is Edward Maddock II in Edmund Street, Liverpool listed as being in Gore's Directory 1815-37. A look at the outer back should solve the date issue.

    Regards,

    Graham
     
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  4. John Matthews

    John Matthews Registered User

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    A nice find.

    In my notes I have T F Cooper operating out of King William Street ~1838 which is at odds with the crowned leopard's head for pre 1822. Are we sure the case is English? - if it is then I would suggest it may have been re-cased.

    In the 1820's he was operating from Wynyat Street ...

    Pigots 1822/23 trade directory

    upload_2019-8-11_19-34-14.png

    I believe that was his earliest address, thereafter he moved to President Street, St Lukes and then Duncan Place, before 18 King William Street.

    As Graham has identified there is a incuse EM maker's mark for Chester believed to be one of the two Edward Maddocks operating in Liverpool. I have checked back to Priestley's source (Ridgeway & Priestley #2113) where there is a photograph of the mark.The font is very similar, but the separation between letters is much smaller in Ridgeway - the two letters are almost touching. The latter looks as if it was made with a single punch whereas on this case the two letters look to me as if they may have been punched separately. With the potential conflict between the address and the presence of the early leopard's head, taken with the absence of a full set of consistent hallmarks, I am leaning to this being an American case. Further photographs should establish whether it is. If it is, it in no way detracts from the movement and to my mind makes the watch all the more interesting for it.

    John
     
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  5. Travler1

    Travler1 Registered User
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    Graham & John ....here’s a sister watch which moved through the simi big Texas auction house ....it is only a few serial numbers off and was described as an 1840 make. We can use that info with a grain of salt included! Apologies for not supplying the back cover pic. It is however exactly the same markings.... one note on the initials which might be more distinctive on the back cover The initials are struck as E. M on both, more clearly seen on back cover. My thoughts were that the movement was US cased with appropriate faux marks ? I definitely bow to your thoughts and resources

    I rigged a stand to hold the watch, used a small torch to view the details ...it is a ruby roller with a steel impulse. Hopefully the roller between the teeth in not terribly chongered up. I assume Graham...that’s why you state English duplexes start their life with ruby rollers, and not always ended that way....I also assume. I’ll keep you posted on the watch’s progress ...thanks a bunch DADBB2F2-37B9-4301-94E2-5CC8C1BF4E66.png
     
  6. John Matthews

    John Matthews Registered User

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    It certainly sounds as if it is an American case. Pleased to hear you have been able to see the ruby roller.

    Very true - particularly as the Heritage Auction listing provides no information regarding how they determined ~1840. I suspect the gold case was also American and precise dating of the case was not possible. It is the address that is key, I understand from my source that he was only at that address for the 2 years until 1838. I suspect the auction house used the address in order to state ~1840 in their description.

    John
     
  7. Lychnobius

    Lychnobius Registered User

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    I am happy for Graham, or anyone else, to correct me if I am wrong, but I believe the domes of English cases were not made with a flat centre (such as we see here) until about 1850; previously they were convex overall. This may mean that the case is American, with faux English marks, and that the crowned leopard is not as true a sign of an early date as it appears to be. The dial and the back plate also suggest the middle of the century to me.

    Oliver Mundy.
     
  8. John Matthews

    John Matthews Registered User

    Sep 22, 2015
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    Oliver

    While I believe you are correct that the flat centre design on British cases is far more commonly found in, and after, the second half of the C19th - they do occur before. Here is a John Williams hunter case with a flat centre from 1826/27.

    Notwithstanding with this particular Cooper duplex, from the evidence so far presented by the owner I think we are safe to infer that the case is American.

    John
     
  9. gmorse

    gmorse Registered User
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    Hi Oliver,

    I'm sure you're right, for the generality of cases, but like so much else in horology, there will always be exceptions, as John has pointed out. However, what we can be more certain about is what the partial hallmarks tell about their veracity, or lack of it.

    Regards,

    Graham
     
  10. Tom McIntyre

    Tom McIntyre Technical Admin
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    I am not sure how much this example contributes to the discussion, but I believe this is a very clear example of a T. F.Cooper duplex in an American case.

    I am trying to recall if I have ever seen an English duplex with a ruby impulse pin. I do have a Jacot star duplex that has both the locking jewel and the impulse jewel.

    If there is a ruby impulse is it a flat stone set in the impulse arm, or is it a jewel rod that replaces the impulse arm in the design?

    Back.jpg CapInside.jpg CapOutside.jpg Cuvette.jpg Face.jpg Front.jpg FrontInside.jpg InnerBackInside.jpg Movement.jpg MovementEdge.jpg
     
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  11. John Matthews

    John Matthews Registered User

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    Tom - I posted one here - this is what it looks like ...

    upload_2019-8-14_7-53-35.png

    upload_2019-8-14_7-54-0.png

    and here is a Cooper example ...

    upload_2019-8-14_8-0-8.png

    John
     
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  12. Tom McIntyre

    Tom McIntyre Technical Admin
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    I try to avoid being stupid, but what is the function of the roller? The long tooth rests on the upright ruby and the long sapphire receives the impulse from the upright duplex teeth.
     
  13. John Matthews

    John Matthews Registered User

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    Tom - I'm sure Graham will jump in and improve, or correct, my thoughts ....

    I assume your question is prompted by to the Cooper roller in the last photograph. I would say that in the first example I posted (signed John Burdett Gibbons) the impulse jewel looks rather vulnerable and could be damaged (particularly during service by someone with limited skills) more easily than the Cooper example, which is protected by the roller into which it is secured.

    John
     
  14. Tom McIntyre

    Tom McIntyre Technical Admin
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    I thought that might be the purpose but it seems to have no function in the operation.

    I wonder if anyone ever jeweled the impulse surface of the more common impulse arm as with a lever pallet set into the arms. That might have the drawback that the arm would have excess mass.

    Another possible use for the roller is to provide a bit better dynamic poise.

    Surely it was discussed way back when> :)
     
  15. gmorse

    gmorse Registered User
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    Hi Tom,

    I feel that's a more likely explanation, plus the circular roller is rather easier to make and what would have been most important, to polish. These design decisions weren't necessarily just empirical, there were some workers with a deep understanding of their craft.

    Regards,

    Graham
     
  16. John Matthews

    John Matthews Registered User

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    Graham - while I agree entirely with the point Tom made regarding the ability to poise and your point that design decisions were driven by understanding, I believe that the 'understanding' would have included a recognition of the resilience of the design in deployment and the background of the maker. It may not be insignificant that the earliest Cooper example with an impulse jewel I have record of is ~1860, I believe the Gibbons signed example to be a little earlier and from the examples I have seen a much rarer design. A design that I suspect did not prove to be resilient. This would explain the rarity, both in terms of the limited period of manufacture and the survival rate of those that were made. The heritage of the Cooper design, I think you would agree, is the single roller, that of the Gibbons is not so obvious to me. It appears to have different influences. Exactly which 'specialist' made these components, we do not know, but they will have determined their design from the totality of their experience.

    Incidentally, while intuitively the Cooper design might look easier to polish in its finished state. I would have thought that (most/all?) of the polishing could have ben done before the jewels were fixed - am I mistaken?

    John
     
  17. gmorse

    gmorse Registered User
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    Hi John,

    Oh yes, it would have been completely polished before being jewelled. Discs are one of the easiest shapes to polish, although there were special swing tools to polish all sorts of odd shapes.

    Regards,

    Graham
     
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  18. Tom McIntyre

    Tom McIntyre Technical Admin
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    upload_2019-8-15_10-18-34.png upload_2019-8-15_10-20-49.png
    upload_2019-8-15_10-22-14.png
    I first saw the jewel impulse arm when preparing a presentation on Charles E. Jacot during his period of being an American maker. I really like the design because it makes the mechanics so obvious. They were not all that successful, of course, and that is why they are seldom seen.
     
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  19. John Matthews

    John Matthews Registered User

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    Tom - while not wishing the discussion of the Jacot star duplex to take over the thread, I would like to understand the correspondence of the clock patent and your description, with the photographs of the actual watch movement. Your description of the patent speaks of the short ruby pins - which I take to be marked '5' on fig 4

    upload_2019-8-15_18-16-42.png

    - but the photograph of what I take to be the escape wheel of the watch, (in the previous slide), appears to be brass.

    upload_2019-8-15_18-17-36.png

    In the same slide the roller with the notch appears to be steel and I cannot decide the material used for the 'impulse arm of the balance', but it may be a jewel.

    upload_2019-8-15_18-14-38.png

    I am interested in exactly how the watch escapement was constructed.

    John
     
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  20. gmorse

    gmorse Registered User
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    Hi John,

    The parts marked '5' are the impulse teeth on the escape wheel and as you state, they do appear to be brass, machined in the normal way for a duplex. The part marked '7' is the impulse 'arm' on the balance, which may be a jewel, although it isn't in the patent drawing.

    I don't understand Tom's statement about the impulse on the Jacot being 'more favourable'; the impulse is being given at a smaller escape wheel radius and a larger balance arm radius.

    Regards,

    Graham
     
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  21. Tom McIntyre

    Tom McIntyre Technical Admin
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    The longer locking tooth provides for less friction on the locking ruby. The longer impulse arm reduces the duration or angular excursion of the impulse event. Those are the primary gains versus the traditional duplex where the same general geometry is in place, but much less extreme.

    The term clock in the patent is not intended to mean in a clock frame, just that it is an escapement for clockworks as opposed to hydraulics maybe. In the patent drawing the impulse pins are jewels and the arm is metal and most likely steel. In the actual model Jacot reversed those two to make the arm a jewel and the pins metal. I do not think he would have considered making them both jewels.

    The point of showing it was to address the time line of the ruby impulse pin. The date of the patent is 1852.
     
  22. gmorse

    gmorse Registered User
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    Hi Tom,

    A smaller impulse duration, (or lift angle), has its down side, because unlike a lever this escapement isn't ever detached, so there's always some friction somewhere. It would tend to reduce the amplitude I'd have thought. In the traditional duplex, the proportions of the two parts are reversed to produce a longer impulse duration.

    Regards,

    Graham
     
  23. Travler1

    Travler1 Registered User
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    Gentlemen, thank you for the knowledge shared and the thoughts provided. I am only the poster ....pls feel free to take the conversations where it leads.

    As far as my watch ...I will post shots of the dial plate, back of dial, as well as the ruby roller and impulse,...plus any requests

    The Cooper is presently at the watchmaker, so now a wait is required.

    Wishing you all the best, thanks again ...John
     
  24. Tom McIntyre

    Tom McIntyre Technical Admin
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    My thought, and I think it was also Jacot's, was that the ratio of diameters of the locking action and impulse action should be as high as feasible in favor of the locking to reduce the friction. The force of the mainspring is expressed in the torque on the duplex wheel arbor. The short leverage arm of the impulse gives greater force to the impulse. The longer arm on the locking means it has a "lighter" touch on the locking jewel while locked (which is essentially all the time.

    It may be more fragile than a standard design, but the mechanics look superior to me. Of course, I am not a watchmaker so I may be missing something.
     
  25. gmorse

    gmorse Registered User
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    Hi Tom,

    I don't think you are, we just look at the problem from different directions. Without a mathematical analysis of the frictional components of Jacot versus traditional duplexes it's impossible to be sure. However, the fact remains that the Jacot remained a frictional rest escapement, in spite of improvements, and as such was an evolutionary dead end at a time when the detached escapements had long established their superiority.

    Sometimes the commercial considerations outweighed all other factors in establishing the success of a design, as evidenced by the small number of Savage escapements as compared to Massey and its descendant the English lever, despite Savage's theoretical advantages. It did continue in limited use for a surprisingly long time, (as did the rack lever for different reasons), so a few makers and customers must have understood its benefits.

    Regards,

    Graham
     
  26. John Matthews

    John Matthews Registered User

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    So my understanding is that with the standard design the ratio of the impulse force to the frictional resistance, due to the force applied by the locking tooth, is smaller than that of the Jacot design, but the impulse force is applied for a longer period in the standard design.

    Is that correct?

    If it is, I cannot intuitively, and certainly not theoretically, rationalise what that would mean to the 'efficiency' of the two designs.

    John
     
  27. gmorse

    gmorse Registered User
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    Hi John,

    George Daniels goes into this in some detail in chapter 8 of 'Watchmaking', where he comments that "The best proportion of the components seems to depend on the fancy of the constructor. No two individually made watches have the same component proportions but the watches exhibit no difference in performance". He goes on to compare the geometries of three fine watches by Breguet, Morice and Jürgensen to demonstrate this, with the ratio of impulse pallet to impulse teeth ranging from 1.5:1 (Breguet), to 2.2:1 (Morice) to 2.6:1 (Jürgensen). He does mention that the friction in Breguet's roller is greater, as might be expected from his lower locking roller to locking teeth ratio, (12.5:1 as opposed to 16:1 and 18:1), and this, together with a reduced impulse angle and larger drops, leads to a greater demand for impulse power. Given that these three watches are a very small sample, Daniels' conclusion on their performance is interesting.

    Regards,

    Graham
     
  28. John Matthews

    John Matthews Registered User

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    #28 John Matthews, Aug 17, 2019 at 2:45 PM
    Last edited: Aug 17, 2019 at 2:50 PM
    Hi Graham - thanks for pointing me to the section in Daniels, which I'm in the process of studying.

    I think you may have made a mistake - the ratios you quote are the impulse teeth to the impulse pallet (D/C)

    My interpretation of the greater friction in the Breguet, compared to that of Jürgensen, is that the friction is inversely proportional to the escape angle (unlocking angle + the smaller impulse angle). Given the quoted unlocking angles i.e. 60 for Breguet and 80 for Jürgensen, I believe it is these that are influential because they are the larger than the impulse angle. The unlocking angle is determined by the intersection of the locking roller circle (A) and the locking teeth circle (B). The smaller the unlocking angle the greater the locking portion of the oscillation which is when the friction occurs. So I conclude that the total frictional resistance that occurs is a function of the normal force applied by the locking teeth and the locking portion of the total arc of vibration, i.e. it is not solely dependent on the force.

    John
     
  29. Tom McIntyre

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    The duration of the friction on the locking roller must be essentially the same on all duplexes. It is present whenever the tooth is resting on the jewel, which is almost all the time. The variable that affects the friction must be the normal force holding the tooth against the jewel.

    During the "backward" free rotation the tooth skips over the unlocking gap, and it is free during impulse but both of those events are very short duration in all of the duplex forms. As a guess I would say a couple percent of the total time between impulses or 98% of the time the locking tooth rests on the jewel.

    In my mind it seems pretty straightforward when viewed from the point of view of the balance rather than the escape wheel. i.e. what does the balance see when all of this is happening?
     
  30. Allan C. Purcell

    Allan C. Purcell Registered User
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    I liked the last paragraph by George Daniels piece on the Duplex escapement.

    " A form or escapement is known as the Chinese duplex has double-locking teeth. Two passing vibrations are required for each impulse vibration. When used with a wheel train of 14,000 vibrations the escapement will indicate one large advancement each second. This system was once held in high esteem by the Chinese who despised crawling seconds hands on their watches. Such escapements are bad timekeepers, but doubtless, the Chinese had sufficient tranquillity of mind not to be concerned."
     
  31. Tom McIntyre

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    I shared that view for a long time and still do for most of the highly decorated movements one sees in these watches.

    Interestingly, Jacot was pursuing a different concept. It seemed important to him that the balance beat at a high frequency and that was the justification for the design. He also made the form with up to 4 micro teeth on the locking tooth. He was exploring the "best" way to apportion the power reserve with multiple oscillations of the balance for each "beat" of the watch.

    He was also the primary proponent of filing patents on watch works in Switzerland.
     
  32. gmorse

    gmorse Registered User
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    Hi John,

    This is indeed D/C.

    And this is B/A.

    The time that the locking tooth spends in contact with the locking roller is certainly constant for a given balance frequency, but the circumferential distance it travels in one cycle depends on the roller's diameter.

    Regards,

    Graham
     
  33. Tom McIntyre

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    All of the locking rollers I have seen are as small as they can practically be and often so small as to be fragile. Do you think there is much difference between them?

    I do not recall seeing any that were "functionally" large. That is to say they seem to be made as small in diameter as they can be.

    The large supporting roller in the Cooper at the beginning of this discussion has no time keeping function in the escapement. I think we both agree that it likely is there to simplify poising.
     
  34. gmorse

    gmorse Registered User
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    Hi Tom,

    The radius of the impulse roller, or rather that of the impulse pallet, (whether it's a jewel or integral with the steel roller), is determined by the difference between the radii of the locking and impulse teeth. I agree that poising is probably the main reason for the most common disc shape.

    Regards,

    Graham
     
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  35. Tom McIntyre

    Tom McIntyre Technical Admin
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    I probably should have said disc instead of roller. The only true roller action is the locking jewel that provides the rest for the locking teeth.

    The duplex is basically a single impulse dead beat escapement. I think it is the most elegant one produced in any quantity. :)
     

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